The research described in this proposal is designed to further our understanding of the molecular components and mechanisms involved in the control of gene expression in bacteria and animal cells. In particular, the multiple control mechanisms involved in the regulation of the isoleucine-valine biosynthetic enzymes in E. coli K12 and asparagine synthetase in Chinese hamster ovary cells will be examined. The effects of tRNA molecules on the regulation of these systems as well as their overall role in protein synthesis will be given special emphasis. Biochemical, genetic and physiological methodologies will be employed in these investigations.